C21 Manipulating Genomes

Question 1

DNA Profiling

21.1 DNA Profiling

Answer 1

• compares introns within the dna to reveal a genetic fingerprint

Question 2

Intron Defenition

21.1 DNA Profiling

Answer 2

dont code for a protein

Question 3

extron definition

21.1 DNA Profiling

Answer 3

codes for a protein

Question 4

Satelite DNA

21.1 DNA Profiling

Answer 4

• a short sequence of dna that repaeats m an hy times within an intron
• known as either VNTRs or STRs epending on size
• the number of repeats varies between individuals
• the closer you are related the sim ilar number of repats youll have

Question 5

How DNA Profiles are Made

21.1 DNA Profiling

Answer 5

1. DNA sample is extracted (and amplified)
2. DNA is digested to break into fragments
3. DNA is seperated using gel electrophoresis
4. sample is visulised through hyhbridisation

Question 6

DNA Extraction

21.1 DNA Profiling

Answer 6

• take a tissue sample e.g cheek swab or blood
• break down the membranes using detergents, enzymes or mechanically
• Use PCR to amplify

Question 7

PCR

21.1 DNA Profiling

Answer 7

Polymerase chain reaction
1. denature
- denaturethe dna by heating to 96
- breaks the hydrogen bonds creating 2 strands.
2. anneal
- anneal the dna by adding two primers
- lower the temp to 55 to allow the primers bond (phosphodiester bonds).
- the primers signal to the polymerase where to start (meaning it c an be specific)
- stops the two strands sticking.
3. synthesis
- 2 dna polymerase molecules attach to the primers and move along the strand
- as they move they c reate complementary dna
- heated to 72 to speed up the reaction
- use TAQ polymerase as humans would denature

every cycle of pcr doubles the dna= initial x 2*n
n= the number of cycles

Question 8

Digestion

21.1 DNA Profiling

Answer 8

• sample is cut into fragments
• uses restricting endonuclease
• this is specific to the targeted area

Question 9

Seperation

21.1 DNA Profiling

Answer 9

• dna is slightly negativley charged
• fragments need to be seperated to be visulised
• the dna is put into wells of aggrose gel
• a current is paszsed through the gel causing the dna to move to the positive charge
• fragments are then seperated by size as the smaller ones will moive further

Question 10

Visulisation

21.1 DNA Profiling

Answer 10

gel is fragile so the fragments are transferred to a nylon membrane through southern blotting
1. alkaline butter used to seperate dna strands
2. dna probes added (hybridisation)
3. stran ds transferred to a nylon sheet
4. nylon sheet has the dna profile and the prob es make it visible

Question 11

DNA Probes

21.1 DNA Profiling

Answer 11

1. isolate the dna
2. denatur4e the sample and combine with the probes (these are complementary to the traget gene and labelled with a molecullar beacon)
3. dna probes will bind to the gene if it is present in the sample

Question 12

Molecular Beacon

21.1 DNA Profiling

Answer 12

radioactive: older tec hnique where it can be seen with x-ray film
flourescent: put the nylon sheet under uv light so the tags glow

Question 13

What are DNA Profiles Used for?

21.1 DNA Profiling

Answer 13

• paternity tests
• phylogeny
• forensics
• breeding programmes
• indentification of those who are at risk to certain diseases